Many people who use hand-held video cameras will move with their cameras to film a scene. Unfortunately, such user movement can cause motion that will undesirably affect the camera's ability to record smooth and pleasing video. Many video cameras have internal mechanisms that substantially eliminate certain types of undesirable effects, such as “shake.” However, these internal mechanisms do not eliminate all types of undesired motion.
For example, moving the camera can induce unwanted motion about the roll, tilt, and pan axes. As seen in FIG. 1, the roll, tilt, and pan axes are defined for clarity as the x, y, and z-axes, respectively. A camera's internal stabilizing mechanisms are not well-suited to address gross motion about these axes. Thus, to eliminate undesired motion about the axes, users typically must employ expensive and complicated camera stabilizers.
Camera stabilizers for video cameras and other optical equipment have been in use for many years. Generally, camera stabilizers are external devices that function to isolate the body of a camera or other optical equipment from the unwanted effects of a user's body movements. Such isolation can eliminate or greatly reduce the undesirable effects in the roll, tilt, and pan directions, thereby providing a smooth video or film recording for the user.
Currently available stabilizers, such as passive inertial stabilizers, generally rely on two principles to achieve smooth video recordings. The first principle uses a mass that connects to, but is spaced away from, the body of the camera. The mass may comprise one or more weights or masses that counterbalance the camera about a pivot point near a center of gravity of the stabilizer. Separating the camera and the mass from the center of gravity increases the moments of inertia of the stabilizer in at least the roll and tilt directions (e.g., the x and y-axes). Thus, a counterbalanced system is more stable in these two axes than the camera is alone. Depending on the distribution of the mass, the counterbalancing mass or masses can also increase a moment of inertia in the pan direction (e.g., z-axis).
The second principle uses gimbals at a support point for the stabilizer structure. As those skilled in the art understand, a gimbal is a pivoted support that permits an object to rotate freely about a single axis. Passive inertial stabilizers typically employ multiple gimbals at a support point on the stabilizer. Each gimbal pivots about a different axis of rotation (e.g., x-axis, y-axis, and z-axis) to allow the stabilizer (and thus, the mounted camera) to rotate about those axes freely. Allowing free rotation in all three axes of rotation effectively isolates the camera from the motions of the user in the roll, tilt, and pan directions.
Users generally prefer balanced camera stabilizers that are slightly bottom-heavy. For example, the mass or masses used to counterbalance the camera may be positioned below the camera such that a center of gravity of the stabilizer is below a point about which the stabilizer pivots. Such stabilizers require little or no operator intervention to maintain the camera parallel to the horizon, which is the most common shot framing position. Even when a camera wanders off-axis, the slightly bottom heavy nature of the stabilizer causes it to automatically return the camera to its original position.
However, bottom-heavy stabilizers usually introduce reaction torques whenever an operator accelerates. That is, with a bottom heavy balance position, any acceleration, including movement in an arc, could produce unwanted motion. Thus, when the operator moves in a direction (e.g., forward), the camera, which mounts to the stabilizer opposite the bottom-heavy portion of the stabilizer, will tend to move in the same direction as the operator (e.g., forward). The slightly bottom-heavy portion of the stabilizer, however, will lag behind the camera. Although the camera will slowly return to its original position, such movement may cause the camera to rock undesirably, and can only be reduced by the skill of the operator. Other conditions and factors, such as wind while filming outdoors or the imperfect design or construction of the stabilizer, can also cause the camera to experience unwanted motion.
To improve camera stability, some manufacturers employ gyroscopes attached directly to the cameras or mounted to a passive stabilizer. For example, Kenyon Laboratories of Higganum, Conn., (http://www.ken-lab.com) sells gyroscopes that mount directly to a camera or camera structure. Other manufacturers, such as Glidecam Industries, Kingston, Mass. (http://www.glidecam.com/products.php) employ gyroscopes supported by a platform that is connected to the camera.
Prior art stabilizers that use gyroscopes, however, are relatively heavy and expensive, and do not provide an optimal combination of platform stabilization and camera control. Further, existing gyroscopes require long startup times and shutdown times, and may restrict an operator's ability to control desired camera movement in the tilt, roll or pan directions. Therefore, prior art stabilizers are not practical for hand-held use.